Altschuler has experience on both sides of the courtroom: when he left in 1998, he was the Chief of the Silicon Valley Branch Office of the U.S. Attorney's Office in Northern California. While working as a U.S. Attorney, Altschuler saw first hand the growing use of data when working Federal criminal cases. Today, as a defense attorney, he believes "online data use is exploding."

[ See also: Facebook's most wanted: Social networking has a dark and hilarious side of ill-conceived criminality. Here are some of Facebook's dimmest crooks (and smartest detectives). ]

Altschuler sees many law enforcement agencies in medium- to large-sized cities either using social media to conduct investigations or gearing up to do so. That's because from the agencies' perspective, there is a vast harvest of information to be reaped, and there are little to no privacy rights extended to persons of interest and suspects online.

How much information can be gathered? Look no further than the 2011 Stanley Cup Riots in Vancouver, BC. By examining hours of video and social media posts made during the event, a taskforce was able to post pictures of over 100 suspected rioters online -- over 30 of which were identified by police.

But it's not just the big events that can be data mined. Even suspects who are quiet, and limit contact on social media only to known friends can be tracked.

"Cops will figure out who the associates of the suspect are," Altschuler explained. The police will then friend or connect to the associates, working to gain their trust, and then will eventually friend the target directly, or be able to glean information about the target through the associates.

In 2007, for example, a detective in Newark, NJ tracked the alleged killers of three college students by mining MySpace pages maintained by the suspects and their friends. In another, pictures and prose posted online by the killer of a 17-year-old Virginia college freshman connected suspect to the victim and revealed where her body was. (See: Cops learn how to walk their beats online)

(Face)book 'em, Dano

A survey of 1,200 federal, state, and local law enforcement professionals by LexisNexis Risk Solutions reveals that using social media as an investigative tool is taking hold. Here's how the numbers stack up.

80% of law enforcement personnel use social media to conduct investigations

67% believe social media helps solve crimes more quickly

87% of the time, search warrants utilizing social media to establish probable cause hold up in court when challenged

Only 10% of respondents had formal training to use social media for investigations